when placing a building where there are obstructing environment elements that need to be destroyed, one must cancel building, navigate to the work GUI, paint a region (from memory) where the ground needs to be cleared, wait (sometimes a long time when workers are busy), and finally go back to the building GUI, and attempt to place the building. (repeat steps where necessary if trees or food spread while you were waiting)

The solution:

when placing a building, allow the purple building indecator to be placed even when there is obstructing terrain. when workers are assigned to work on this building, if there is obstructing terrain, make them clear it first. Simple. Place and forget.